The general principles of operation for a plasma mass filter that is designed to separate low-mass particles from high-mass particles are disclosed in co-pending application Ser. No. 09/192,945 now U.S. Pat. No. 6,096,228 which was filed on Nov. 16, 1998 for an invention entitled "Plasma Mass Filter" and which is assigned to the same assignee as the present invention. In short, a plasma mass filter includes a cylindrical shaped wall which surrounds a hollow chamber. A magnet is mounted on the wall to generate a magnetic field that is aligned substantially parallel to the longitudinal axis of the chamber. Also, an electric field is generated within the chamber which is oriented substantially perpendicular to the magnetic field. Importantly, for operation of a plasma filter, the electric field has a positive potential on the axis relative to the wall which is usually at a zero potential. When a multi-species plasma is injected into the chamber, the plasma interacts with the crossed magnetic and electric fields, resulting in the bulk rotation of the plasma about the chamber axis.
As disclosed in co-pending application entitled "Plasma Mass Filter" and referenced above, the density of the plasma inside the filter is maintained low to avoid particle collisions within the filter. In particular, the plasma density is controlled so that the ratio of each particle's cyclotron frequency (.OMEGA.) to the particle's collision frequency (.nu.) exceeds one (.OMEGA./.nu.&gt;1). Specifically, in response to the crossed magnetic and electric fields, each ionized or charged particle in the multi-species plasma will travel on a circular orbit in a plane that is substantially perpendicular to the magnetic field lines. The size of this orbit, or orbit radius, is dependent on the mass to charge ratio of the orbiting particle. Accordingly, the plasma mass filter is designed so that high-mass particles will travel on orbits that are so large that the high-mass particles will strike and be captured by the wall surrounding the chamber. On the other hand, the low-mass particles will have orbits that are smaller than the chamber radius, and hence are confined inside the chamber so as not to strike the chamber walls. Thus, the orbiting low-mass particles drift in the direction of the magnetic field lines, and eventually exit the chamber at one end of the cylinder. The device of the present invention is a collector cup that is designed to collect and remove the low-mass particles that exit from the plasma mass filter.
In light of the above it is an object of the present invention to provide a collector cup which can be positioned in fluid communication with a plasma mass filter for the collection and removal of the low-mass particles that exit from the filter. It is another object of the present invention to provide a collector cup with features that allow for the efficient removal of material that has become deposited on the collector surface. Yet another object of the present invention is to provide a collector cup which is easy to use, relatively simple to manufacture, and comparatively cost effective.